The present invention relates to medical devices, and in particular, to medical devices for grasping and manipulating bones. More particularly, the present invention relates to a lever for grasping and manipulating the fragments of a fractured bone, including the proximal fragment of a fractured femur.
Fractures of the proximal femoral shaft have proven difficult to manipulate in preparation for internal fixation. For example, when proximal shaft fractures of the femur occur, the distal end of the proximal fragment rotates anterior (flexion) and lateral (abduction) creating difficulty in accessing the piriformis fossa, the desired entry point for intramedullary nailing or other methods of internal fixation.
Several devices for aligning fractured bones are described in the prior art. For example, U.S. Pat. Nos. 5,133,342 to Seaton and 5,733,291 to Guidera et al. describe bone alignment levers that are applied to the exterior of the patient""s leg and maneuvered to align portions of a fractured bone. These external devices, however, do not provide adequate manipulation of the bone to rotate fractured bone portions such as the proximal femoral shaft back into proper alignment.
Internal devices for aligning fractured bones are also described in the prior art. One example is U.S. Pat. No. 5,312,412 to Whipple, which describes a fixation alignment guide that includes an axially movable shaft having a bone engagement arm extending outwardly therefrom for engaging a fractured bone at a first surface location. A tubular guide through which the shaft is inserted includes jaws opposing the bone engagement arm for engaging the fractured bone at a second surface location. A ratchet mechanism and cooperating ratchet teeth are operatively associated with the guide for securing the bone engagement arm at a desired distance from the jaws to fixedly engage the fractured bone therebetween. The jaws and engagement arm are spaced apart laterally and define a large profile that requires a large incision for insertion into the patient. In addition, the ratchet mechanism and ratchet teeth only provide for incremental adjustment of the distance between the jaws and the engagement arm, and thus limit the user""s ability to precisely adjust the amount of force applied to the bone.
Another fixation alignment guide is described in U.S. Pat. No. 5,690,640 to Gotfried. This device includes a first hook for gripping the rear surface of the bone and a screw-threaded bar and handle which extend to the outside of the limb. A second hook for gripping a connector plate is movable on the bar. The two hooks are pulled together by a winged nut screwed onto the bar, thereby pressing the plate onto the bone. Similar to the Whipple device, discussed above, the two hooks require a large incision for insertion into the patient. Also, the speed at which the distance between the hooks can be adjusted is limited by the user""s ability to quickly tighten or loosen the winged nut, thus limiting the ability to quickly apply or release the device in case of an emergency.
Thus, there remains a need for a lever that provides adequate rotation of a bone, for example, the femur, requires a small incision for insertion into the patient, provides precise adjustment of the force applied to the bone, and may be quickly applied and removed from the bone.
The present invention is directed to a lever for grasping bone tissue. The lever includes a shaft defining a channel, a claw member disposed on an end of the shaft for holding the bone tissue, and a rod threadably received in the channel. Rotation of the rod with respect to the shaft also causes the rod to move substantially axially with respect to the shaft to selectively position the distal end of the rod with respect to the claw member. The channel may include a first threaded portion and the rod may include a second threaded portion for threadably engaging the first threaded portion. The lever may include a bone engaging tip disposed on the distal end of the rod, which tip may be pointed, substantially concave, pivotable, or any other configuration known to one of ordinary skill in the art. The claw member may include a pair of spaced apart talons for grasping the bone tissue. The lever may further include an adjustment knob disposed on the rod. Additionally, a handle may be disposed on an end of the shaft.
According to another embodiment of the invention, the lever includes a locking member defining a second channel substantially aligned with the first channel. The locking member is moveable between a first position wherein the rod is axially slidable in the first channel, and a second position wherein the rod is substantially prevented from axial sliding in the first channel. When the locking member is in the second position, the locking member threadably engages the rod such that rotation of the rod with respect to the shaft causes the rod to move substantially axially with respect to the shaft. The locking member may include a first threaded portion, the rod may include a second threaded portion, and the locking member may be resiliently biased toward the rod such that the first threaded portion engages the second threaded portion. Alternatively, the locking member may be rotatable with respect to the rod between the first and second positions such that when the locking member is in the first position the first threaded portion is disengaged from the second threaded portion, and when the locking member is in the second position the first threaded portion engages the second threaded portion.
According to yet another embodiment of the present invention, the lever includes a handle portion and the claw member is removably and replaceably associated with the handle portion. The handle portion may include a shaft, and the claw member may be removably and replaceably associated with an end of the shaft. Alternatively, the claw member may include a shaft, and an end of the shaft may be removably and replaceably associated with the handle portion. The lever may further include a set of claw members, each of the claw members having different properties.
The present invention is further directed to a method of using the lever to align first and second portions of a fractured bone. The method includes the steps of inserting at least a portion of the lever into an incision near the fractured bone, positioning the claw member around the first portion of the fractured bone, positioning the rod to engage the bone first portion between the rod and the claw member, and maneuvering the bone lever to align the first portion of the bone with the second portion of the bone. The method may also include the step of rotating the rod.